Wireless communication system, base station apparatus, mobile station apparatus, wireless communication method and integrated circuit

ABSTRACT

When a common search space and a user equipment-specific search space overlap with each other, and bit numbers of DCI formats transmitted in the common search space and the user equipment-specific search space, respectively are the same as each other, a mobile station apparatus identifies a type of the DCI format. When the common search space and the user equipment-specific search space overlap with each other, and a bit number of a DCI format allocated in the common search space and a bit number of a DCI format allocated in the user equipment-specific search space are the same as each other, a base station apparatus does not allocate the DCI format allocated in the user equipment-specific search space in the overlapped space, and a mobile station apparatus performs blind decoding only of the DCI format allocated in the common search space in the overlapped space.

TECHNICAL FIELD

The present invention relates to a wireless communication system, a basestation apparatus, a mobile station apparatus, a wireless communicationmethod, and an integrated circuit.

BACKGROUND ART

In 3GPP (3rd Generation Partnership Project), has been examinedevolution of a radio access system and a radio network of cellularmobile communication (hereinafter referred to as “LTE (Long TermEvolution) ” or “EUTRA (Evolved Universal Terrestrial Radio Access)”).In the LTE, an OFDM (Orthogonal Frequency Division Multiplexing) system,which is multicarrier transmission, is used as a communication systemfor wireless communication from a base station apparatus to a mobilestation apparatus (downlink). In addition, an SC-FDMA (Single-CarrierFrequency Division Multiple Access) system, which is single careertransmission, is used as a communication system for wirelesscommunication from the mobile station apparatus to the base stationapparatus (uplink).

In the LTE, the base station apparatus decides radio resourceassignment, a coding rate, a modulation scheme, etc. of a PUSCH(Physical Uplink Shared Channel), which is the channel for datatransmission transmitted by the mobile station apparatus and of a PDSCH(Physical Downlink Shared Channel), which is the channel for datatransmission transmitted by the base station apparatus. In addition, thebase station apparatus transmits DCI (Downlink Control Information)indicating the radio resource assignment to the mobile station apparatususing a PDCCH (Physical Downlink Control Channel).

Hereinafter, the PDCCH will be described in more detail. The PDCCH isallocated in one or more CCEs (Control Channel Elements). The CCE is aunit of a radio resource in which the PDCCH is allocated. In addition, acommon search space and a user equipment-specific search space arecomprised of the plurality of CCEs.

The common search space is the space common among the plurality ofmobile station apparatuses, and is the space where the PDCCH for theplurality of mobile station apparatuses and/or the PDCCH for a specificmobile station apparatus are allocated. The common search space iscomprised of a predetermined CCE. The user equipment-specific searchspace is the space where the PDCCH for the specific mobile stationapparatus is allocated, and is the space configured for each mobilestation apparatus. As for the common search space and the userequipment-specific search space, different common search space and userequipment-specific search space are configured for each number of theCCEs in which the PDCCH is allocated. Note that apart or all of thecommon search space and the user equipment-specific search space mayoverlap with each other, a part or all of the different common searchspaces may overlap with each other, a part or all of the different userequipment-specific search spaces for the same mobile station apparatusmay overlap with each other, and that a part or all of the userequipment-specific search spaces for the different mobile stationapparatuses may overlap with each other.

A plurality of formats is prepared for DCI transmitted by the PDCCH. Aformat of the DCI is called a DCI format. In the DCI formats, there areincluded a DCI format with a same bit number (or also referred to as a“payload size”) as the other DCI formats, and a DCI format with adifferent bit number from the other DCI formats. The base stationapparatus adds to the DCI a sequence in which a CRC (Cyclic RedundancyCheck) code generated based on the DCI is scrambled (or referred to asmasked) by RNTI (Radio Network Temporary Identity).

The mobile station apparatus changes an interpretation of the DCIdepending on by which RNTI the CRC code is scrambled. Hereinafter, astate where the CRC code scrambled by the RNTI has been added to the DCIwill be represented simply as that the RNTI is included in the DCI, orthe RNTI is included in the PDCCH. For example, the mobile stationapparatus discriminates a type of the DCI format of the DCI from theRNTI included in the DCI.

The base station apparatus encodes the DCI according to the bit numberof the CCE, and allocates it in the common search space or the userequipment-specific search space. Note that the base station apparatusperforms the same coding of DCI formats with a same bit number, and thatperforms different coding of DCI formats with different bit numbers.Namely, since a coding scheme which the base station apparatus appliesto the DCI format differs depending on the bit number of the DCI format,a decoding method of the DCI format in the mobile station apparatusdiffers depending on the bit number of the DCI format. Accordingly, themobile station apparatus can discriminate the type of the DCI formatbased on a difference of the bit number of the DCI format, or of thedecoding method. When the bit number of the DCI format is the same aseach other, the mobile station apparatus is made to be able todiscriminate the type of the DCI format by using a method for includingin the DCI format information for discriminating the type of the DCIformat, or for adding a CRC code scrambled by RNTI corresponding to thetype of the DCI format, etc.

When the mobile station apparatus performs decoding processing of allthe CCE candidates in which the PDCCH is allocated in the common searchspace and the user equipment-specific search space, further descramblesby the RNTI a sequence in which the CRC code has been scrambled by theRNTI, and detects no error in the descrambled CRC code, it determines tohave succeeded in obtaining the PDCCH. This processing is called blinddecoding.

In addition, in the 3GPP, has been examined a radio access system and aradio network that achieves higher-speed data communication (hereinafterreferred to as “LTE-A (Long Term Evolution-Advanced)” or “A-EUTRA(Advanced Evolved Universal Terrestrial Radio Access)”) utilizing awider frequency band than the LTE. It is required that the LTE-A hasbackward compatibility with the LTE, i.e., a base station apparatus ofthe LTE-A simultaneously performs wireless communication with mobilestation apparatuses of both the LTE-A and the LTE, and the mobilestation apparatus of the LTE-A can perform wireless communication withbase station apparatuses of both the LTE-A and the LTE, and it has beenexamined that a same channel structure as in the LTE is used for theLTE-A.

In the LTE-A, has been examined a technology (frequency bandaggregation, also referred to as spectrum aggregation, carrieraggregation, frequency aggregation, etc.) in which a plurality offrequency bands (hereinafter referred to as “CCs (Component Carriers)”)with the same channel structure as in the LTE are used as one frequencyband (wide frequency band). Specifically, in communication using thefrequency band aggregation, a downlink channel is transmitted for eachdownlink CC, and an uplink channel is transmitted for each uplink CC.Namely, frequency band aggregation is a technology in which a basestation apparatus and a plurality of mobile station apparatusessimultaneously transmit and receive a plurality of data information anda plurality of control information using a plurality of carriercomponents including a plurality of channels in an uplink and adownlink.

CITATION LIST Non-Patent Document

Non-Patent Document 1: “3GPP TS36.213 v.9.0.1 (2009-December)”,2009-12-18.

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, there has been a problem in a conventional technology that amobile station apparatus cannot identify a type of a DCI format when acommon search space and a user equipment-specific search space overlapwith each other, i.e., CCE candidates in which PDCCHs of the commonsearch space and the user equipment-specific search space are allocatedare comprised of the same number and of the same radio resources,further RNLI included in the PDCCHs is the same as each other, and bitnumbers of the DCI formats transmitted in the common search space andthe user equipment-specific search space, respectively are the same aseach other.

The present invention is made in view of the above-described problem,and an object of the present invention is to provide a wirelesscommunication system in which a mobile station apparatus can identify atype of a DCI format, a base station apparatus, a mobile stationapparatus, a wireless communication method, and an integrated circuit inthe wireless communication system in which a common search space and auser equipment-specific search space overlap with each other,

Means for Solving the Problems

(1) In order to achieve the above-described object, the presentinvention has taken the following measures. Namely, a wirelesscommunication system of the present invention is the wirelesscommunication system comprising a mobile station apparatus and a basestation apparatus which transmits control information to the mobilestation apparatus, and the wireless communication system ischaracterized in that when payload sizes of respective controlinformation of a physical downlink control channel candidate of a commonsearch space and a physical downlink control channel candidate of amobile station control-specific search space, the physical downlinkcontrol channel candidates being the candidates in which the controlinformation is allocated, are the same as each other, and the physicaldownlink control channel candidate of the common search space and thephysical downlink control channel candidate of the userequipment-specific search space are comprised of same CCEs, the basestation apparatus allocates the control information only in the physicaldownlink control channel candidate of the common search space andtransmits the control information, and the mobile station apparatusperforms reception processing of the control information determiningthat the control information has been transmitted using the physicaldownlink control channel only in the common search space.

(2) In addition, a wireless communication system of the presentinvention is characterized in that CRC of the control information isscrambled by C-RNTI.

(3) In addition, a wireless communication system of the presentinvention is characterized in that the base station apparatus and themobile station apparatus communicate with each other using a pluralityof CCs, and that the control information includes information indicatinga CC to which the physical downlink control channel corresponds.

(4) In addition, a wireless communication system of the presentinvention is characterized in that the base station apparatus and themobile station apparatus communicate with each other using a pluralityof CCs, and that the common search space and the user equipment-specificsearch space are configured in a same CC.

(5) In addition, a base station apparatus of the present invention isthe base station apparatus which transmits control information to amobile station apparatus, and the base station apparatus ischaracterized in that when payload sizes of respective controlinformation of a physical downlink control channel candidate of a commonsearch space and a physical downlink control channel candidate of amobile station control-specific search space, the physical downlinkcontrol channel candidates being the candidates in which the controlinformation is allocated, are the same as each other, and the physicaldownlink control channel candidate of the common search space and thephysical downlink control channel candidate of the userequipment-specific search space are comprised of same CCEs, the basestation apparatus allocates the control information only in the physicaldownlink control channel candidate of the common search space andtransmits the control information.

(6) In addition, a base station apparatus of the present invention ischaracterized in that CRC of the control information is scrambled byC-RNTI.

(7) In addition, a base station apparatus of the present invention ischaracterized in that the base station apparatus communicates with themobile station apparatus using a plurality of CCs, and that the controlinformation includes information indicating a CC to which the physicaldownlink control channel corresponds.

(8) In addition, a base station apparatus of the present invention ischaracterized in that the base station apparatus communicates with themobile station apparatus using a plurality of CCs, and that the commonsearch space and the user equipment-specific search space are configuredin a same CC.

(9) In addition, a mobile station apparatus of the present invention isthe mobile station apparatus which receives control informationtransmitted from a base station apparatus, and the mobile stationapparatus is characterized in that when in the base station apparatus,payload sizes of respective control information of a physical downlinkcontrol channel candidate of a common search space and a physicaldownlink control channel candidate of a mobile station control-specificsearch space, the physical downlink control channel candidates being thecandidates in which the control information is allocated, are the sameas each other, and the physical downlink control channel candidate ofthe common search space and the physical downlink control channelcandidate of the user equipment-specific search space are comprised ofsame CCEs, the mobile station apparatus performs reception processing ofthe control information determining that the control information hasbeen transmitted using the physical downlink control channel only in thecommon search space.

(10) In addition, it is characterized in that CRC of the controlinformation is scrambled by C-RNTI.

(11) In addition, a mobile station apparatus of the present invention ischaracterized in that the mobile station apparatus communicates with thebase station apparatus using a plurality of CCs, and that the controlinformation includes information indicating a CC to which the physicaldownlink control channel corresponds.

(12) In addition, a mobile station apparatus of the present invention ischaracterized in that the mobile station apparatus communicates with thebase station apparatus using a plurality of CCs, and that the commonsearch space and the user equipment-specific search space are configuredin a same CC.

(13) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, and the wireless communication method is characterized inthat when payload sizes of respective control information of a physicaldownlink control channel candidate of a common search space and aphysical downlink control channel candidate of a mobile stationcontrol-specific search space, the physical downlink control channelcandidates being the candidates in which the control information isallocated, are the same as each other, and the physical downlink controlchannel candidate of the common search space and the physical downlinkcontrol channel candidate of the user equipment-specific search spaceare comprised of same CCEs, the base station apparatus allocates thecontrol information only in the physical downlink control channelcandidate of the common search space and transmits the controlinformation.

(14) In addition, a wireless communication method of the presentinvention is characterized in that CRC of the control information isscrambled by C-RNTI.

(15) In addition, a wireless communication method of the presentinvention is characterized in that the base station apparatuscommunicates with the mobile station apparatus using a plurality of CCs,and that the control information includes information indicating a CC towhich the physical downlink control channel corresponds.

(16) In addition, a wireless communication method of the presentinvention is characterized in that the base station apparatuscommunicates with the mobile station apparatus using a plurality of CCs,and that the common search space and the user equipment-specific searchspace are configured in a same CC.

(17) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a mobile stationapparatus which receives control information transmitted from a basestation apparatus, and the wireless communication method ischaracterized in that when in the base station apparatus, payload sizesof respective control information of a physical downlink control channelcandidate of a common search space and a physical downlink controlchannel candidate of a mobile station control-specific search space, thephysical downlink control channel candidates being the candidates inwhich the control information is allocated, are the same as each other,and the physical downlink control channel candidate of the common searchspace and the physical downlink control channel candidate of the userequipment-specific search space are comprised of same CCEs, the mobilestation apparatus performs reception processing of the controlinformation determining that the control information has beentransmitted using the physical downlink control channel only in thecommon search space.

(18) In addition, a wireless communication method of the presentinvention is characterized in that CRC of the control information isscrambled by C-RNTI.

(19) In addition, a wireless communication method of the presentinvention is characterized in that the mobile station apparatuscommunicates with the base station apparatus using a plurality of CCs,and that the control information includes information indicating a CC towhich the physical downlink control channel corresponds.

(20) In addition, a wireless communication method of the presentinvention is characterized in that the mobile station apparatuscommunicates with the base station apparatus using a plurality of CCs,and that the common search space and the user equipment-specific searchspace are configured in a same CC.

(21) In addition, an integrated circuit of the present invention is theintegrated circuit used for a base station apparatus which transmitscontrol information to a mobile station apparatus, and the integratedcircuit is characterized in that when payload sizes of respectivecontrol information of a physical downlink control channel candidate ofa common search space and a physical downlink control channel candidateof a mobile station control-specific search space, the physical downlinkcontrol channel candidates being the candidates in which the controlinformation is allocated, are the same as each other, and the physicaldownlink control channel candidate of the common search space and thephysical downlink control channel candidate of the userequipment-specific search space are comprised of same CCEs, the basestation apparatus allocates the control information only in the physicaldownlink control channel candidate of the common search space andtransmits the control information.

(22) In addition, an integrated circuit of the present invention ischaracterized in that CRC of the control information is scrambled byC-RNTI.

(23) In addition, an integrated circuit of the present invention ischaracterized in that the base station apparatus communicates with themobile station apparatus using a plurality of CCs, and that the controlinformation includes information indicating a CC to which the physicaldownlink control channel corresponds.

(24) In addition, an integrated circuit of the present invention ischaracterized in that the base station apparatus communicates with themobile station apparatus using a plurality of CCs, and that the commonsearch space and the user equipment-specific search space are configuredin a same CC.

(25) In addition, an integrated circuit of the present invention is theintegrated circuit used for a mobile station apparatus which receivescontrol information transmitted from a base station apparatus, and theintegrated circuit is characterized in that when in the base stationapparatus, payload sizes of respective control information of a physicaldownlink control channel candidate of a common search space and aphysical downlink control channel candidate of a mobile stationcontrol-specific search space, the physical downlink control channelcandidates being the candidates in which the control information isallocated, are the same as each other, and the physical downlink controlchannel candidate of the common search space and the physical downlinkcontrol channel candidate of the user equipment-specific search spaceare comprised of same CCEs, the mobile station apparatus performsreception processing of the control information determining that thecontrol information has been transmitted using the physical downlinkcontrol channel only in the common search space.

(26) In addition, an integrated circuit of the present invention ischaracterized in that CRC of the control information is scrambled byC-RNTI.

(27) In addition, an integrated circuit of the present invention ischaracterized in that the mobile station apparatus communicates with thebase station apparatus using a plurality of CCs, and that the controlinformation includes information indicating a CC to which the physicaldownlink control channel corresponds.

(28) In addition, an integrated circuit of the present invention ischaracterized in that the mobile station apparatus communicates with thebase station apparatus using a plurality of CCs, and that the commonsearch space and the user equipment-specific search space are configuredin a same CC.

(29) In addition, a wireless communication system of the presentinvention is the wireless communication system comprising a mobilestation apparatus and a base station apparatus which transmits controlinformation to the mobile station apparatus, and the wirelesscommunication system is characterized in that when an information bitnumber of a first format which is the format of the control informationand which includes information indicating a CC is a predetermined bitnumber, the base station apparatus inserts at least 1 bit in the firstformat to decide a first payload size, and transmits the first format ofthe first payload size to the mobile station apparatus, and the mobilestation apparatus performs reception processing of the first formatdetermining that the first format is the first payload size.

(30) In addition, a base station apparatus of the present invention isthe base station apparatus which transmits control information to amobile station apparatus, and the base station apparatus ischaracterized in that when an information bit number of a first formatwhich is the format of the control information and which includesinformation indicating a CC is a predetermined bit number, the basestation apparatus inserts at least 1 bit in the first format to decide afirst payload size, and transmits the first format of the first payloadsize to the mobile station apparatus.

(31) In addition, a mobile station apparatus of the present invention isthe mobile station apparatus which receives control informationtransmitted from a base station apparatus, and the mobile stationapparatus is characterized in that the mobile station apparatus receivesa first format determining that the first format which is the format ofthe control information and which includes information indicating a CCis a first payload size decided by the base station apparatus insertingat least 1 bit in the first format.

(32) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, and the wireless communication method is characterized bycomprising the steps of: inserting at least 1 bit in a first format todecide a first payload size; and transmitting the first format of thefirst payload size to the mobile station apparatus when an informationbit number of the first format which is the format of the controlinformation and which includes information indicating a CC is apredetermined bit number.

(33) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a mobile stationapparatus which receives control information transmitted from a basestation apparatus, and the wireless communication method ischaracterized by comprising a step of receiving a first formatdetermining that the first format which is the format of the controlinformation and which includes information indicating a CC is a firstpayload size decided by the base station apparatus inserting at least 1bit in the first format.

(34) In addition, an integrated circuit of the present invention is theintegrated circuit used for a base station apparatus which transmitscontrol information to a mobile station apparatus, and the integratedcircuit is characterized by comprising: a function for inserting atleast 1 bit in a first format to decide a first payload size; and afunction for transmitting the first format of the first payload size tothe mobile station apparatus when an information bit number of the firstformat which is the format of the control information and which includesinformation indicating a CC is a predetermined bit number.

(35) In addition, an integrated circuit of the present invention is theintegrated circuit used for a mobile station apparatus which receivescontrol information transmitted from a base station apparatus, and theintegrated circuit is characterized by comprising a function forreceiving a first format determining that the first format which is theformat of the control information and which includes informationindicating a CC is a first payload size decided by the base stationapparatus inserting at least 1 bit in the first format.

(36) In addition, a wireless communication system of the presentinvention is the wireless communication system comprising a mobilestation apparatus and a base station apparatus which transmits controlinformation to the mobile station apparatus, and the wirelesscommunication system is characterized in that the base station apparatusand the mobile station apparatus configure a common search space from apredetermined CCE, configure a user equipment-specific search space inwhich the number of CCEs configuring a PDCCH candidate is the same asthat of the common search space from the CCEs excluding the CCEs usedfor the common search space, and that configure from all the CCEs a userequipment-specific search space in which the number of CCEs configuringthe PDCCH candidate is different from that of the common search space.

(37) In addition, a base station apparatus of the present invention isthe base station apparatus which transmits control information to amobile station apparatus, and the base station apparatus ischaracterized in that the base station apparatus configures a commonsearch space from a predetermined CCE, configures a userequipment-specific search space in which the number of CCEs configuringa PDCCH candidate is the same as that of the common search space fromthe CCEs excluding the CCEs used for the common search space, and thatconfigure from all the CCEs a user equipment-specific search space inwhich the number of CCEs configuring the PDCCH candidate is differentfrom that of the common search space.

(38) In addition, a mobile station apparatus of the present invention isthe mobile station apparatus which receives control informationtransmitted from a base station apparatus, and the mobile stationapparatus is characterized in that the mobile station apparatusconfigures a common search space from a predetermined CCE, configures auser equipment-specific search space in which the number of CCEsconfiguring a PDCCH candidate is the same as that of the common searchspace from the CCEs excluding the CCEs used for the common search space,and that configures from all the CCEs a user equipment-specific searchspace in which the number of CCEs configuring the PDCCH candidate isdifferent from that of the common search space.

(39) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, and the wireless communication method is characterized bycomprising the steps of: configuring a common search space from apredetermined CCE; configuring a user equipment-specific search space inwhich the number of CCEs configuring a PDCCH candidate is the same asthat of the common search space from the CCEs excluding the CCEs usedfor the common search space; and configuring from all the CCEs a userequipment-specific search space in which the number of CCEs configuringthe PDCCH candidate is different from that of the common search space.

(40) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a mobile stationapparatus which receives control information transmitted from a basestation apparatus, and the wireless communication method ischaracterized by comprising the steps of: configuring a common searchspace from a predetermined CCE; configuring a user equipment-specificsearch space in which the number of CCEs configuring a PDCCH candidateis the same as that of the common search space from the CCEs excludingthe CCEs used for the common search space; and configuring from all theCCEs a user equipment-specific search space in which the number of CCEsconfiguring the PDCCH candidate is different from that of the commonsearch space.

(41) In addition, an integrated circuit of the present invention is theintegrated circuit used for a base station apparatus which transmitscontrol information to a mobile station apparatus, and the integratedcircuit is characterized by comprising: a function for configuring acommon search space from a predetermined CCE; a function for configuringa user equipment-specific search space in which the number of CCEsconfiguring a PDCCH candidate is the same as that of the common searchspace from the CCEs excluding the CCEs used for the common search space;and a function for configuring from all the CCEs a userequipment-specific search space in which the number of CCEs configuringthe PDCCH candidate is different from that of the common search space.

(42) In addition, an integrated circuit of the present invention is theintegrated circuit used for a mobile station apparatus which receivescontrol information transmitted from a base station apparatus, and theintegrated circuit is characterized by comprising: a function forconfiguring a common search space from a predetermined CCE; a functionfor configuring a user equipment-specific search space in which thenumber of CCEs configuring a PDCCH candidate is the same as that of thecommon search space from the CCEs excluding the CCEs used for the commonsearch space; and a function for configuring from all the CCEs a userequipment-specific search space in which the number of CCEs configuringthe PDCCH candidate is different from that of the common search space.

ADVANTAGE OF THE INVENTION

According to the invention, a mobile station apparatus can identify atype of a DCI format.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual illustration of a wireless communication systemaccording to a first embodiment of the present invention;

FIG. 2 is a diagram showing one example of frequency band aggregationprocessing of the present invention;

FIG. 3 is a schematic diagram showing one example of a configuration ofa downlink radio frame of the present invention;

FIG. 4 is a schematic diagram showing one example of a search space ofthe present invention;

FIG. 5 is a schematic diagram showing a coding method and an allocationmethod of DCI of the present invention;

FIG. 6 is a flow chart showing one example of operations of a mobilestation apparatus 1 and a base station apparatus 3 of the presentinvention;

FIG. 7 is a schematic block diagram showing a configuration of the basestation apparatus 3 of the present invention;

FIG. 8 is a schematic block diagram showing a configuration of themobile station apparatus 1 of the present invention; and

FIG. 9 is a schematic diagram showing one example of a search spaceaccording to a third embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, a first embodiment of the present invention will bedescribed in detail with reference to drawings.

FIG. 1 is a conceptual illustration of a wireless communication systemaccording to a first embodiment of the present invention. In FIG. 1, thewireless communication system comprises mobile station apparatuses 1A to1C and a base station apparatus 3. FIG. 1 shows that in wirelesscommunication from the base station apparatus 3 to mobile stationapparatuses 1A to 1C (downlink), assigned are an SCH (SynchronizationChannel), a downlink pilot channel (or, also referred to as a “DL RS(Downlink Reference Signal)”), a PBCH (Physical Broadcast Channel), aPDCCH (Physical Downlink Control Channel), a PDSCH (Physical DownlinkShared Channel), a PMCH (Physical Multicast Channel), a PCFICH (PhysicalControl Format Indicator Channel), and a PHICH (Physical Hybrid ARQIndicator Channel).

In addition, FIG. 1 shows that in wireless communication from the mobilestation apparatuses 1A to 1C to the base station apparatus 3 (uplink),assigned are an uplink pilot channel (or, also referred to as an “UL RS(Uplink Reference Signal)”), a PUCCH (Physical Uplink Control Channel),a PUSCH (Physical Uplink Shared Channel), a PRACH (Physical RandomAccess Channel). Hereinafter, the mobile station apparatuses 1A to 1Care referred to as a mobile station apparatus 1.

FIG. 2 is a diagram showing one example of frequency band aggregationprocessing of the present invention. In FIG. 2, a horizontal axisindicates a frequency domain and a vertical axis indicates a timedomain. As shown in FIG. 2, a downlink subframe D1 is comprised ofsubframes of three downlink CCs (a DL CC-1 (Downlink ComponentCarrier-1), a DL CC-2, and a DL CC-3) each having a bandwidth of 20 MHz.To each of the subframes of the downlink CCs, time-multiplexed are aspace which is indicated by a space hatched with lattice-shaped linesand in which a PDCCH is allocated, and a space which is indicated by aspace without hatching and in which a PDSCH is allocated. For example,the base station apparatus 3 allocates a signal in the PDSCHs of one ormore downlink CCs of the three downlink CCs in a certain downlinksubframe, and transmits the signal to the mobile station apparatus 1.

Meanwhile, an uplink subframe U1 is comprised of three uplink CCs (a ULCC-1 (Uplink Component Carrier-1), a UL CC-2, and a UL CC-3) each havinga bandwidth of 20 MHz. To each of the subframes of the uplink CCs,frequency-multiplexed are a space which is indicated by a space hatchedwith oblique lattice-shaped lines and in which a PUCCH is allocated, anda space which is indicated by a space hatched with rising oblique linesfrom bottom left to top right and in which a PUSCH is allocated. Forexample, the mobile station apparatus 1 allocates a signal in the PUSCHsof one or more uplink CCs of the three uplink CCs in a certain uplinksubframe, and transmits the signal to the base station apparatus 3

FIG. 3 is a schematic diagram showing one example of a configuration ofa downlink radio frame of the present invention. FIG. 3 shows theconfiguration of the radio frame in a certain downlink CC. In FIG. 3, ahorizontal axis indicates a time domain and a vertical axis indicates afrequency domain. As shown in FIG. 3, the radio frame of the downlink CCis comprised of a plurality of downlink PRB (Physical Resource Block)pairs (for example, a space surrounded with a dashed line in FIG. 3).This downlink PRB pair is a unit of radio resource assignment, etc., andis comprised of a frequency band (PRB bandwidth; 180 kHz) with apredetermined width and a time zone (two slots are equal to onesubframe; 1 ms).

One downlink PRB pair is comprised of two downlink PRBs (PRB bandwidth×aslot) contiguous in the time domain. One downlink PRB (a unit surroundedwith a thick line in FIG. 3) is comprised of twelve subcarriers (15 kHz)in the frequency domain, and is comprised of seven OFDM (OrthogonalFrequency Division Multiplexing) symbols (71 μs) in the time domain.

In the time domain, there exists a slot (0.5 ms) comprised of the sevenOFDM symbols (71 μs), a subframe (1 ms) comprised of two slots, and aradio frame (10 ms) comprised of ten subframes. In the frequency domain,the plurality of downlink PRBs is allocated according to a bandwidth ofthe downlink CC. Note that a unit comprised of one subcarrier and oneOFDM symbol is referred to as a downlink resource element.

Hereinafter, a channel which is assigned in the downlink radio framewill be described. In each downlink subframe, for example, a PDCCH, aPDSCH, and a DL RS are assigned. First, the PDCCH will be described. ThePDCCH is first allocated in OFDM symbols of a head of a subframe (spacehatched with the rising oblique lines from bottom left to top right inFIG. 3). Note that the number of OFDM symbols in which the PDCCH isallocated is one to three, and differs for each subframe. In the PDCCH,allocated is a signal of DCI (Downlink Control Information) which iscomprised of information formats, such as downlink assignment (alsoreferred to as downlink grant) and uplink grant, and which isinformation used for controlling communication.

The downlink assignment is comprised information indicating a modulationscheme for the PDSCH, information indicating a coding scheme,information indicating radio resource assignment, information regardinga HARQ (Hybrid Automatic Repeat Request), a TPC command, etc. Inaddition, the uplink grant is comprised of information indicating amodulation scheme for the PUSCH, information indicating a coding scheme,information indicating radio resource assignment, information regardinga HARQ, a TPC command, etc. Note that the HARQ is a technology in whichfor example, when the mobile station apparatus 1 (base station apparatus3) transmits success or failure (ACK/NACK (Acknowledgement/NegativeAcknowledgement)) of decoding of data information to the base stationapparatus 3 (mobile station apparatus 1), and the mobile stationapparatus 1 (base station apparatus 3) cannot decode data informationdue to an error (NACK), the base station apparatus 3 (mobile stationapparatus 1) retransmits a signal, and the mobile station apparatus 1(base station apparatus 3) performs decoding processing with respect toa composite signal of the signal received again and the already receivedsignal.

Next, the PDSCH will be described. The PDSCH is allocated in OFDMsymbols (space without hatching in FIG. 2) other than the OFDM symbolsin which the PDCCH is allocated in the subframe. A signal of datainformation (Transport Block) is allocated in the PDSCH. A radioresource of the PDSCH is assigned using downlink assignment. The radioresource of the PDSCH is allocated in a same downlink subframe as thePDCCH including the downlink assignment having used for assignment ofthe PDSCH in the time domain, and is allocated in a same downlink CC anda different downlink CC as/from the PDCCH including the downlinkassignment having used for assignment of the PDSCH in the frequencydomain.

In the PDCCH, included is information (hereinafter referred to as a“carrier indicator”) indicating to which PDSCH transmitted by a downlinkCC the downlink assignment corresponds, or to which PUSCH transmitted byan uplink CC the uplink assignment corresponds. When the carrierindicator is not included in the downlink assignment, the downlinkassignment corresponds to a PDSCH of the same downlink CC in which thedownlink assignment has been transmitted. When the carrier indicator isnot included in the uplink grant, the uplink grant corresponds to aPUSCH of an uplink CC linked to the same downlink CC in which the uplinkgrant has been transmitted. Although an illustration of a DL RS isomitted in FIG. 2 for simplifying a description, the DL RS isdistributedly allocated in the frequency domain and the time domain.

Hereinafter, the PDCCH will be described in more detail. The PDCCH isallocated in one or more CCEs (Control Channel Elements). The CCE iscomprised of a plurality of downlink resource elements which aredistributed in the frequency domain and the time domain within the space(space hatched with the rising oblique lines from bottom left to topright in FIG. 3) in which the PDCCH is allocated. In addition, a commonsearch space and a user equipment specific-search space are comprised ofthe plurality of CCEs.

FIG. 4 is a schematic diagram showing one example of a search space ofthe present invention. In FIG. 4, a horizontal axis indicates the numberto identify a CCE. A unit surrounded by a thick line in FIG. 4 is acandidate (hereinafter referred to as a “PDCCH candidate”) which iscomprised of a plurality of contiguous number of CCEs, and in which thePDCCH is allocated, a PDCCH candidate hatched by rising oblique linesfrom bottom left to top right in FIG. 4 is the PDCCH candidate for theuser equipment-specific search space, and a PDCCH candidate hatched byfalling oblique lines from top left to bottom right in FIG. 4 is thePDCCH candidate for the common search space.

The common search space is the space common between the plurality ofmobile station apparatuses 1, and is the space where the PDCCH for theplurality of mobile station apparatuses 1 and/or the PDCCH for aspecific mobile station apparatus 1 is allocated. In addition, thecommon search space is comprised of predetermined CCEs, and the commonsearch space is comprised of CCEs of No. 0 to No. 15 in FIG. 4. The userequipment-specific search space is the space where the PDCCH for thespecific mobile station apparatus 1 is allocated, and is the spaceconfigured for each mobile station apparatus 1.

The common search space and the user equipment-specific search spacediffer for each number of CCEs which configure the PDCCH candidates. InFIG. 4, there are four different user equipment-specific search spacesfor a PDCCH candidate comprised of one CCE, a PDCCH candidate comprisedof two CCEs, a PDCCH candidate comprised of four CCEs, a PDCCH candidatecomprised of eight CCEs, and there are two different common searchspaces for a PDCCH candidate comprised of four CCEs, and a PDCCHcandidate comprised of eight CCEs.

Note that a part of the CCEs, or a part or all of the PDCCH candidateswhich configure the common search space and the user equipment-specificsearch space may overlap with each other, a part or all of the differentcommon search spaces may overlap with each other, a part or all of thedifferent user equipment-specific search spaces for the same mobilestation apparatus 1 may overlap with each other, and that a part or allof the user equipment-specific search spaces for the different mobilestation apparatuses 1 may overlap with each other.

Note that the base station apparatus 3 configures a common search spacefor each downlink CC. In addition, the base station apparatus 3 mayallocate one or more downlink CCs which monitor the common search spacefor each mobile station apparatus 1 to inform the mobile stationapparatus 1 of the assigned downlink CCs. Note that the base stationapparatus 3 may allocate one or more downlink CCs which configure theuser equipment-specific search space for each mobile station apparatus 1to inform the mobile station apparatus 1 of the assigned downlink CCs.

A plurality of formats is prepared for the DCI, such as downlink grantand uplink grant. A format of the DCI is called a DCI format. Forexample, for a DCI format of the uplink grant, prepared are a DCI format0 used when the mobile station apparatus 1 transmits a PUSCH through onetransmission antenna port, a DCI format 0A used when the mobile stationapparatus 1 transmits the PUSCH by MIMO (Multiple Input Multiple Output)SM (Spatial Multiplexing), etc.

In addition, for a DCI format of the downlink grant, prepared are a DCIformat 1 used when the base station apparatus 3 transmits the PDSCHthrough one transmission antenna port or the plurality of transmissionantenna ports using a transmission diversity scheme and a DCI format 1Awith fewer bit numbers than the DCI format 1 (DCI format includinginformation regarding one transport block) and a DCI format 1C with muchfewer bit numbers than the DCI format 1A, the DCI format 1C being usedfor radio resource assignment, such as paging information, a DCI format2 used when the base station apparatus 3 transmits the PDSCH by MIMO SM(a DCI format including information regarding one or more transportblocks), etc. Bit numbers of the DCI format 1 and the DCI format 1A andthe DCI format 1C, and the DCI format 2 change depending on the numberof PRBs included inn dowlink CC to which each DCI format corresponds,and bit numbers of the DCI format 0 and the DCI format 0A changedepending on the number of PRBs included in the uplink CC to which eachDCI format corresponds.

Sizes of the two DCI format 0 and DCI format 1A are made to be the sameones by inserting a bit in the format with smaller bit numbers, andflags for identifying the format is included in the formats. A formatobtained by inserting the bit to make the bit sizes of the DCI format 0and the DCI format 1A same is called a DCI format 0/1A.

The DCI format 1C can be allocated only in the common search space. TheDCI format 0/1A not including a carrier indicator can be allocated inboth the common search space and the user equipment-specific searchspace. The DCI format 0/1A including the carrier indicator can beallocated only in the user equipment-specific search space. The DCIformat 0A and the DCI format 2 can be allocated only in the userequipment-specific search space in both cases of not including andincluding the carrier indicator.

FIG. 5 is a schematic diagram showing a coding method and an allocationmethod of DCI of the present invention. First, the base stationapparatus 3 adds to the DCI a sequence in which a CRC (Cyclic RedundancyCheck) code generated based on the DCI is scrambled by RNTI (RadioNetwork Temporary Identity). The mobile station apparatus 1 changes aninterpretation of the DCI depending on with which RNTI the CRC code isscrambled. For example, when the CRC code is scrambled by C-RNTI(Cell-Radio Network Temporary Identity) assigned to the mobile stationapparatus 1 itself from the base station apparatus 3, the mobile stationapparatus 1 determines that the DCI is the information indicating aradio resource addressed to the mobile station apparatus 1 itself.Hereinafter, a state where the CRC code scrambled with the RNTI has beenadded to the DCI will be represented simply as that the RNTI is includedin the DCI, or the RNTI is included in the PDCCH.

Next, the base station apparatus 3 encodes the DCI according to the bitnumber of a PDCCH candidate in which the encoded DCI is allocated, andallocates the encoded DCI in a PDCCH candidate of the common searchspace or the user equipment-specific search space. Note that the basestation apparatus 3 performs the same coding of DCI formats of the samebit number, and that performs different coding of DCI formats of thedifferent bit numbers. Namely, since a coding scheme applied to a DCIformat by the base station apparatus 3 differs depending on a bit number(or, also referred to as a “payload size”) of the DCI format, a decodingmethod of the DCI format in the mobile station apparatus 1 differsdepending on the bit number of the DCI format. Accordingly, the mobilestation apparatus 1 can discriminate a type of the DCI format by adifference of the bit number of the DCI format, or of the decodingmethod. When the bit number of the DCI format is the same as each other,the mobile station apparatus 1 is made to discriminate the type of theDCI format using a method for including in the DCI format informationfor discriminating the type thereof, or a method for adding a CRC codescrambled by RNTI corresponding to the type of the DCI format.

When the mobile station apparatus 1 performs decoding processing of allthe candidates in which the PDCCH is allocated in the common searchspace and the user equipment-specific search space, further descramblesby RNTI a sequence in which a CRC code has been scrambled by the RNTI,and detects to have no error in the descrambled CRC code, it determinesto have succeeded in obtaining the PDCCH. This processing is calledblind decoding.

The base station apparatus 3 allocates in the common search space aPDCCH including P-RNTI (Paging-Radio Network Temporary Identity) usedfor scheduling of paging information and update information of systeminformation, and a PDCCH including SI-RNTI (System Information-RadioNetwork Temporary Identity) used for scheduling of the systeminformation, and a PDCCH including RA-RNTI (Random Access-Radio NetworkTemporary Identity) used for scheduling of a random access response, andthe mobile station apparatus 1 performs blind decoding of the PDCCHincluding the P-RNTI, the PDCCH including the SI-RNTI, and the PDCCHincluding the RA-RNTI in the common search space. The P-RNTI, theSI-RNTI, and the RA-RNTI are included only in the DCI format 1C and theDCI format 1A.

The base station apparatus 3 allocates the PDCCH including the C-RNTI inthe common search space or in the user equipment-specific search spaceof the mobile station apparatus 1 to which the base station apparatus 3has assigned the C-RNTI, and the mobile station apparatus 1 performsblind decoding of the PDCCH including the C-RNTI in the common searchspace and the user equipment-specific search space. Specifically, thebase station apparatus 3 allocates a DCI format 0/1A including C-RNTIand not including a carrier indicator in the common search space or inthe user equipment-specific search space of the mobile station apparatus1 to which the base station apparatus 3 has assigned the C-RNTI, andallocates a DCI format 0/1A including C-RNTI and including a carrierindicator, and a DCI format 0A including the C-RNTI, and a DCI format 2including the C-RNTI in the user equipment-specific search space of themobile station apparatus 1 to which the base station apparatus 3 hasassigned the C-RNTI.

Note that the base station apparatus 3 can indicate, to each mobilestation apparatus 1, for each downlink CC a type of the DCI format towhich the mobile station apparatus 1 performs blind decoding, andwhether or not the carrier indicator is included in the DCI formatallocated in the user equipment-specific search space.

FIG. 6 is a flow chart showing one example of operations of the mobilestation apparatus 1 and the base station apparatus 3 of the presentinvention. FIG. 6 is the flow chart for illustrating a method forcalculating a bit number of a DCI format, and the mobile stationapparatus 1 and the base station apparatus 3 calculate the bit number ofthe DCI format with the same method. When processing is started, themobile station apparatus 1 and the base station apparatus 3 calculatebit numbers of a field indicating radio resource assignment of a DCIformat, etc. based on a number of PRBs included in a downlink CC, anumber of PRBs included in an uplink CC, whether or not a carrierindicator is included in the DCI format, etc., and they calculate a bitnumber of a DCI format indicating radio resource assignment of a PDSCHor a PUSCH (step S100).

The mobile station apparatus 1 and the base station apparatus 3determine whether or not the DCI format is allocated in a space wherethe common search space and the user equipment-specific search spaceoverlap with each other (step S101). Note that overlapping of the commonsearch space and the user equipment-specific search space means thatPDCCH candidates comprised of the same number of CCEs are included inboth the common search space and the user equipment-specific searchspace as a PDCCH candidate comprised of the CCEs of No. 8 to No. 15 inFIG. 4. When the DCI format is not allocated in the space where thecommon search space and the user equipment-specific search space overlapwith each other in step S101, the mobile station apparatus 1 and thebase station apparatus 3 complete processing regarding calculation ofthe bit number of the DCI format.

When the DCI format is allocated in the space where the common searchspace and the user equipment-specific search space overlap with eachother in step S101, the mobile station apparatus 1 and the base stationapparatus 3 compare the bit numbers of the respective DCI formatscalculated in step S100 (step S102). When all the bit numbers of therespective DCI formats calculated in step S100 are different from eachother in step S102, the mobile station apparatus 1 and the base stationapparatus 3 complete processing regarding calculation of the bit numberof the DCI format. Namely, even for the same DCI format, the mobilestation apparatus 1 and the base station apparatus 3 switch whether toinsert a bit depending on whether the DCI format is allocated in thespace where the common search space and the user equipment-specificsearch space overlap with each other, or whether it is allocated in aspace where the common search space and the user equipment-specificsearch space do not overlap with each other.

When the bit numbers of the respective DCI formats calculated in stepS100 are the same as each other, and there is a DCI format to beallocated in the space where the common search space and the userequipment-specific search space overlap with each other in step S102,the mobile station apparatus 1 and the base station apparatus 3 insert 1bit in either of the DCI formats (step S103), and the program returns tostep S102 to compare again the bit number of the DCI format in which thebit has been inserted with that of the other DCI format. Note that it ispreviously decided in which DCI format the mobile station apparatus 1and the base station apparatus 3 insert the bit. Namely, a priority ofthe DCI format in which the bit is inserted is previously decided.

For example, assume that the bit number of the DCI format 0/1A notincluding the carrier indicator which the mobile station apparatus 1 andthe base station apparatus 3 have calculated in step S100 is 40 bits,the bit number of the DCI format 0/1A, including the carrier indicatoris 40 bits, and that the bit number of the DCI format 2 including thecarrier indicator is 40 bits. When PRBs included in the downlink CC andthe uplink CC to which the DCI format 0/1A including the carrierindicator corresponds are less than PRBs included in the downlink CC andthe uplink CC to which the DCI format 0/1A not including the carrierindicator corresponds, a bit number (information bit number) of the DCIformat 0/1A not including the carrier indicator and a bit number(information bit number) of the DCI format 0/1A including the carrierindicator may become the same as each other.

In step S103, an order to insert a bit is the order of the DCI format0/1A allocated in the common search space, the DCI format 0/1A allocatedin the user equipment-specific search space, and the DCI format 2allocated in the user equipment-specific search space, and the mobilestation apparatus 1 and the base station apparatus 3 store this order.In step S101, when the respective DCI formats are not allocated in thespace where the common search space and the user equipment-specificsearch space overlap with each other, the mobile station apparatus 1 andthe base station apparatus 3 use the bit numbers of the respective DCIformats calculated in step S100 as they are.

In step S102, since the bit number of the DCI format 0/1A which does notinclude the carrier indicator and which is allocated in the commonsearch space, and the bit number of the DCI format 0/1A including thecarrier indicator which is allocated in the user equipment-specificsearch space are respectively the same 40 bits, the mobile stationapparatus 1 and the base station apparatus 3 insert 1 bit in the DCIformat 0/1A including the carrier indicator which is allocated in theuser equipment-specific search space (step S103), change the bit numberof the DCI format 0/1A to 41 bits, and the program returns to step S102.

If the program returns to step S102, the mobile station apparatus 1 andthe base station apparatus 3 insert 1 bit in the DCI format 2 which isallocated in the user equipment-specific search space (step S103),change the bit number of the DCI format 2 to 41 bits, and the programreturns to step S102 since the bit number of the DCI format 0/1Aincluding the carrier indicator which is allocated in the common searchspace, and the bit number of the DCI format 2 which is allocated in theuser equipment-specific search space are respectively the same 40 bits.

If the program returns to step S102, the mobile station apparatus 1 andthe base station apparatus 3 insert 1 bit in the DCI format 2 includingthe carrier indicator which is allocated in the user equipment-specificsearch space (step S103), change the bit number of the DCI format 2 to42 bits, and the program returns to step S102 since the bit number ofthe DCI format 0/1A including the carrier indicator which is allocatedin the user equipment-specific search space, and the bit number of theDCI format 2 including the carrier indicator which is allocated in theuser equipment-specific search space are respectively the same 41 bits.

After the above-described step, since the bit number of the DCI format0/1A not including the carrier indicator is 40 bits (a second payloadsize), the bit number of the DCI format 0/1A including the carrierindicator is 41 bits (the first payload size), the bit number of the DCIformat 2 including the carrier indicator is 42 bits (the first payloadsize), and thus the bit numbers of the respective DCI formats are notthe same as each other, the mobile station apparatus 1 and the basestation apparatus 3 complete processing regarding calculation of the bitnumber of the DCI format.

As described above, the mobile station apparatus 1 and the base stationapparatus 3 give priority to insertion of a bit in the DCI formatallocated in the user equipment-specific search space and/or the DCIformat including the carrier indicator over the DCI format allocated inthe common search space so that the bit is not inserted in the DCIformat allocated in the common search space, whereby the bit numbers ofthe DCI formats allocated in the common search space can be made to bethe same between the mobile station apparatuses 1.

Note that since the DCI format can be identified from a value indicatedby the carrier indicator when the values indicated by the respectivecarrier indicators of the DCI format 0/1A including the carrierindicator which is allocated in the user equipment-specific searchspace, and of the DCI format 2 including the carrier indicator which isallocated in the user equipment-specific search space are different fromeach other, the mobile station apparatus 1 and the base stationapparatus 3 do not insert the bit in the DCI format 2 including thecarrier indicator which is allocated in the user equipment-specificsearch space. Namely, the mobile station apparatus 1 and the basestation apparatus 3 decide whether or not to insert the bit depending onwhether the values indicated by the carrier indicators included in therespective two DCI formats of the same bit number are the same as eachother or are different from each other.

The base station apparatus 3 generates a DCI format of the bit number ofthe DCI format calculated according to the flow chart of FIG. 6, encodesand modulates it, and transmits it through the PDCCH. The mobile stationapparatus 1 performs blind decoding of the DCI format of the bit numberof the DCI format calculated according to the flow chart of FIG. 6. Notethat the mobile station apparatus 1 and the base station apparatus 3 maycalculate the bit number of a DCI format for each subframe according tothe flow chart of FIG. 6, and that may store the bit numbers previouslycalculated with respect to combinations of various DCI formats.

Note that step S101 may be omitted in the flow chart of FIG. 6. When thebit numbers of the DCI format allocated in the common search space andthe DCI format allocated in the user equipment-specific search space arethe same as each other regardless of overlapping or non-overlapping ofthe common search space and the user equipment-specific search space dueto omission of step S101, a bit is inserted in the DCI format allocatedin the user equipment-specific search space. As a result of this,although an unnecessary bit is inserted also in the DCI format allocatedin the user equipment-specific search space which does not overlap withthe common search space, apparatus configurations of the mobile stationapparatus 1 and the base station apparatus 3 can be simplified.

FIG. 7 is a schematic block diagram showing a configuration of the basestation apparatus 3 of the present invention. As shown in the drawing,the base station apparatus 3 is configured to include an higher layerprocessing unit 101, a control unit 103, a reception unit 105, atransmission unit 107, a channel measurement unit 109, and atransmission/reception antenna 111. In addition, the higher layerprocessing unit 101 is configured to include a radio resource controlunit 1011, a scheduling unit 1013, and a DCI generation unit 1015. Inaddition, the reception unit 105 is configured to include a decodingunit 1051, a demodulation unit 1053, a demultiplexing unit 1055, and aradio reception unit 1057. In addition, the transmission unit 107 isconfigured to include a coding unit 1071, a modulation unit 1073, amultiplexing unit 1075, a radio transmission unit 1077, and a DL RSgeneration unit 1079.

The higher layer processing unit 101 performs processing of a PDCP(Packet Data Convergence Protocol) layer, an RLC (Radio Link Control)layer, and an RRC (Radio Resource Control) layer. In addition, thehigher layer processing unit 101 generate control information in orderto control the reception unit 105 and the transmission unit 107 based ona scheduling result of the scheduling unit 1013 etc., and output thecontrol information to the control unit 103. The radio resource controlunit 1011 comprised in the higher layer processing unit 101 generatesinformation to be allocated in a downlink PDSCH, or obtains it from anhigher node, and outputs it to the transmission unit 107. In addition,the radio resource control unit 1011 manages various setting informationof each mobile station apparatus 1. For example, the radio resourcecontrol unit 1011 manages RNTI, such as assignment of C-RNTI to themobile station apparatus 1.

The scheduling unit 1013 comprised in the higher layer processing unit101 performs scheduling, such as radio resource assignment, setting of acoding scheme, and setting of a modulation scheme based on uplinkcontrol information (ACK/NACK, channel quality information, a schedulingrequest) informed through the PUCCH from the mobile station apparatus 1,and a buffer condition informed from the mobile station apparatus 1 andvarious setting information of the each mobile station apparatus 1 setby the radio resource control unit 1011. The scheduling unit 1013allocates a radio resource in which a specific mobile station apparatus1 allocates the PUSCH among uplink radio resources. The scheduling unit1013 gives priority to assignment of a radio resource with a goodchannel quality based on an uplink channel measurement result havinginput from the channel measurement unit 109 in allocating the radioresource in which the PUSCH is allocated to the specific mobile stationapparatus 1.

In addition, the scheduling unit 1013 decides a radio resource in whichthe PDSCH is allocated among downlink radio resources. The schedulingunit 1013 outputs control information to the DCI generation unit 1015 sothat the DCI generation unit 1015 may generate DCI indicating the radioresource assignment. In addition, the scheduling unit 1013 allocates aPDCCH candidate in which DCI having generated by the DCI generation unit1015 is allocated from the common search space or the userequipment-specific search space. The scheduling unit 1013 selects aPDCCH candidate in which DCI including C-RNTI is allocated from the userequipment-specific search space of the mobile station apparatus 1 towhich the C-RNTI has been assigned and the common search space.

The DCI generation unit 1015 comprised in the higher layer processingunit 101 generates DCI indicating uplink or downlink radio resourceassignment based on the control information input from the schedulingunit 1013. The DCI generation unit 1015 inserts a bit in the DCIaccording to the flow chart of FIG. 6. Next, the DCI generation unit1015 generates a CRC code from the generated DCI, and scrambles thegenerated CRC code with RNTI, and adds it to the DCI. When the DCI isthe information indicating the radio resource assignment to the specificmobile station apparatus 1, the DCI generation unit 1015 scrambles theCRC code by the C-RNTI assigned to the mobile station apparatus 1.

The control unit 103 generates a control signal which performs controlof the reception unit 105 and the transmission unit 107 based on thecontrol information from the higher layer processing unit 101. Thecontrol unit 103 outputs the generated control signal to the receptionunit 105 and the transmission unit 107, and performs control of thereception unit 105 and the transmission unit 107.

The reception unit 105 separates, demodulates, and decodes the receivedsignal received from the mobile station apparatus 1 through thetransmission/reception antenna 111 according to the control signal inputfrom the control unit 103, and outputs the decoded information to thehigher layer processing unit 101. The radio reception unit 1057 converts(down-converts) into an intermediate frequency the uplink signalreceived through the transmission/reception antenna 111, removes anunnecessary frequency component, controls an amplification level so thata signal level is maintained appropriately, orthogonally demodulates thesignal based on an in-phase component and an orthogonal component of thereceived signal, and converts the orthogonally demodulated analog signalinto a digital signal. The radio reception unit 1057 removes a portioncorresponding to a GI (Guard Interval) from the converted digitalsignal. The radio reception unit 1057 performs FFT (Fast FourierTransform) with respect to the signal from which the GI has beenremoved, extracts a signal in the frequency domain, and outputs it tothe demultiplexing unit 1055.

The demultiplexing unit 1055 separates the signal input from the radioreception unit 1057 into signals, such as a PUCCH, a PUSCH, and a UL RS.Note that this separation is performed based on the radio resourceassignment information which the base station apparatus 3 has previouslydecided in the scheduling unit 1013 and has informed each mobile stationapparatus 1. In addition, the demultiplexing unit 1055 compensates achannel of the PUCCH and the PUSCH from an estimate value input from thechannel measurement unit 109. In addition, the demultiplexing unit 1055outputs the separated UL RS to the channel measurement unit 109.

The demodulation unit 1053 performs IDFT (Inverse Discrete FourierTransform) of the PUSCH, obtains a modulation symbol, and demodulatesthe received signal with respect to each modulation symbol of the PUCCHand the PUSCH using a predetermined modulation scheme or a modulationscheme which the base station apparatus 3 has previously informed theeach mobile station apparatus 1 by downlink control information, such asBPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying),16 QAM (16 Quadrature Amplitude Modulation), and 64 QAM (64 QuadratureAmplitude Modulation).

The decoding unit 1051 decodes encoded bits of the demodulated PUCCH andthe PUSCH using a coding rate of a predetermined coding scheme, thecoding rate being a predetermined or previously informed to the mobilestation apparatus 1 by the base station apparatus 3 in the uplink grant,and outputs the decoded data information and the uplink controlinformation to the higher layer processing unit 101. The channelmeasurement unit 109 measures an estimate value of the channel, achannel quality, etc. from the UL RS input from the demultiplexing unit1055, and outputs them to the demultiplexing unit 1055 and the higherlayer processing unit 101.

The transmission unit 107 generates a DL RS according to the controlsignal input from the control unit 103, encodes and modulates the datainformation and the DCI which have been input from the higher layerprocessing unit 101, multiplexes the PDCCH, the PDSCH, and the DL RS,and transmits the signal to the mobile station apparatus 1 through thetransmission/reception antenna 111.

The coding unit 1071 performs coding, such as turbo coding, convolutioncoding, and block coding, which is previously set or decided by thescheduling unit 1013, of the DCI and the data information input from thehigher layer processing unit 101. The modulation unit 1073 modulates anencoded bit input from the coding unit 1071 with a modulation scheme,such as QPSK, 16 QAM, and 64 QAM, which is previously set or decided bythe scheduling unit 1013. The DL RS generation unit 1079 generates as aDL RS a known sequence of the mobile station apparatus 1 which can becalculated by a rule predetermined based on a cell ID for identifyingthe base station apparatus 3. The multiplexing unit 1075 multiplexeseach modulated channel and the generated DL RS.

The radio transmission unit 1077 performs IFFT (Inverse Fast FourierTransform) of the multiplexed modulation symbol to thereby performmodulation of an OFDM scheme, adds a GI to the OFDM-modulated OFDMsymbol, generates a digital signal of a baseband, converts the digitalsignal of the baseband into an analog signal, generates an in-phasecomponent and an orthogonal component of an intermediate frequency fromthe analog signal, removes an excessive frequency component with respectto an intermediate frequency band, converts (up-converts) a signal withthe intermediate frequency into a signal with a high frequency, removesan excessive frequency component, amplifies power, and outputs thesignal to the transmission/reception antenna 111 to transmit.

FIG. 8 is a schematic block diagram showing a configuration of themobile station apparatus 1 of the present invention. As shown in thedrawing, the mobile station apparatus 1 is configured to include anhigher layer processing unit 201, a control unit 203, a reception unit205, a transmission unit 207, a channel measurement unit 209, and atransmission/reception antenna 211. In addition, the higher layerprocessing unit 201 is configured to include a radio resource controlunit 2011, a scheduling unit 2013, and a blind decoding control unit2015. In addition, the reception unit 205 is configured to include adecoding unit 2051, a demodulation unit 2053, a demultiplexing unit2055, and a radio reception unit 2057. In addition, the transmissionunit 207 is configured to include a coding unit 2071, a modulation unit2073, a multiplexing unit 2075, a radio transmission unit 2077, and a DLRS generation unit 2079.

The higher layer processing unit 201 outputs uplink data informationgenerated by user operation etc.

to the transmission unit 207. In addition, the higher layer processingunit 201 performs processing of the PDCP layer, the RLC layer, and theRRC layer. In addition, the higher layer processing unit 201 generatescontrol information in order to control the reception unit 205 and thetransmission unit 207 based on the DCI etc., and outputs the controlinformation to the control unit 203. The radio resource control unit2011 comprised in the higher layer processing unit 201 manages varioussetting information of the mobile station apparatus 1 itself. Forexample, the radio resource control unit 2011 manages RNTI, such asC-RNTI. In addition, the radio resource control unit 2011 generatesinformation to be allocated in each uplink channel, and outputs it tothe transmission unit 207.

The blind decoding control unit 2015 comprised in the higher layerprocessing unit 201 generates control information for controlling thereception unit 205 so that the reception unit 205 may perform blinddecoding of the DCI of a DCI format to be detected by the mobile stationapparatus 1 in the common search space and/or the userequipment-specific search space, and outputs the control information tothe control unit 203. The blind decoding control unit 2015 generatescontrol information for controlling the reception unit 205 so thatreception unit 205 may perform blind decoding of the PDCCH including theC-RNTI in the common search space and the user equipment-specific searchspace, and outputs the control information to the control unit 203. Inaddition, the blind decoding control unit 2015 calculates as a bit ofDCI a bit number of the DCI format to which blind decoding is performedaccording to the flow chart of FIG. 6.

The scheduling unit 2013 comprised in the higher layer processing unit201 generates control information in order to control the reception unit205 and the transmission unit 207 based on the DCI informed through thePDCCH from the base station apparatus 3, and various setting informationof the mobile station apparatus 1 itself which the radio resourcecontrol unit 2011 set by a radio resource control signal informedthrough the PDSCH, and outputs the control information to the controlunit 203. The scheduling unit 2013 controls the reception unit 205 sothat the mobile station apparatus 1 may perform multiplex separation,demodulation, and decoding of the PDSCH based on downlink assignmentinput from the reception unit 205, generates control information forcontrolling the transmission unit 207 so that the mobile stationapparatus 1 may perform coding of PUSCH, modulation, and multiplex ofthe PUSCH based on uplink grant input from the reception unit 205, andoutputs the control information to the control unit 203.

The control unit 203 generates a control signal which performs controlof the reception unit 205 and the transmission unit 207 based on thecontrol information from the higher layer processing unit 201. Thecontrol unit 203 outputs the generated control signal to the receptionunit 205 and the transmission unit 207, and performs control of thereception unit 205 and the transmission unit 207. The reception unit 205separates, demodulates, and decodes the received signal received fromthe base station apparatus 3 through the transmission/reception antenna211 according to the control signal input from the control unit 203, andoutputs the decoded information to the higher layer processing unit 101.

The radio reception unit 2057 converts (down-converts) into anintermediate frequency the downlink signal received through thetransmission/reception antenna 211, removes an unnecessary frequencycomponent, controls an amplification level so that a signal level may bemaintained appropriately, orthogonally demodulates the signal based onan in-phase component and an orthogonal component of the receivedsignal, and converts the orthogonally demodulated analog signal into adigital signal. The radio reception unit 2057 removes a portioncorresponding to a GI from the converted digital signal, performs FFTwith respect to the signal from which the GI has been removed, andextracts signals of the frequency domain.

The demultiplexing unit 2055 separates the extracted signals into aPDCCH, a PDSCH, and a DL RS, respectively. Note that this separation isperformed based on the radio resource assignment information informed bythe DCI. In addition, the demultiplexing unit 2055 compensates a channelof the PUCCH and the PUSCH from an estimate value input from the channelmeasurement unit 209. In addition, the demultiplexing unit 2055 outputsthe separated DL RS to the channel measurement unit 209.

The demodulation unit 2053 demodulates the PDCCH in a QPSK modulationscheme, and outputs it to the decoding unit 2051. When the decoding unit2051 tried blind decoding of the PDCCH to succeed in the blind decoding,it outputs the decoded DCI and the RNTI included in the DCI to thehigher layer processing unit 201. The demodulation unit 2053 demodulatesthe PDSCH in the modulation scheme informed by the DCI, such as QPSK, 16QAM, and 64 QAM, and outputs it to the decoding unit 2051. The decodingunit 2051 decodes a coding rate informed by the DCI, and outputs thedecoded data information to the higher layer processing unit 201.

The channel measurement unit 209 measures a downlink path loss from theDL RS input from the demultiplexing unit 2055, and outputs the measuredpath loss to the higher layer processing unit 201. In addition, thechannel measurement unit 209 calculates an estimate value of a downlinkchannel from the DL RS, and outputs it to the demultiplexing unit 2055.

The transmission unit 207 generates a UL RS according to the controlsignal input from the control unit 203, encodes and modulates the datainformation input from the higher layer processing unit 201, multiplexesthe PUCCH, the PUSCH, and the generated UL RS, and transmits them to thebase station apparatus 3 through the transmission/reception antenna 211.The coding unit 2071 encodes the uplink control information input fromthe higher layer processing unit 201 using convolution coding, blockcoding, etc., and performs turbo coding of the data information based onthe coding rate informed by the DCI. The modulation unit 2073 modulatesthe encoded bit input from the coding unit 2071 with a modulation schemeinformed by DCI, such as BPSK, QPSK, 16QAM, or a modulation schemepredetermined for each channel.

The UL RS generation unit 2079 generates a known sequence of the basestation apparatus 3 which can be calculated by a rule predeterminedbased on a cell ID for identifying the base station apparatus 3, abandwidth in which the UL RS is allocated, etc. The multiplexing unit2075 performs DFT (Discrete Fourier Transform) after reallocating themodulation symbols of the PUSCH in parallel according to the controlsignal input from the control unit 203, and multiplexes the signals ofthe PUCCH and the PUSCH, and the generated UL RS.

The radio transmission unit 2077 performs IFFT of the multiplexed signalto thereby perform modulation of an SC-FDMA scheme, adds a GI to theSC-FDMA-modulated SC-FDMA symbol, generates a digital signal of abaseband, converts the digital signal of the baseband into an analogsignal, generates an in-phase component and an orthogonal component ofan intermediate frequency from the analog signal, removes an excessivefrequency component with respect to an intermediate frequency band,converts (up-converts) a signal with the intermediate frequency into asignal with a high frequency, removes an excessive frequency component,amplifies power, and outputs the signal to the transmission/receptionantenna 211 to transmit.

As described above, according to the present invention, in a wirelesscommunication system comprising a plurality of mobile stationapparatuses 1 and a base station apparatus 3 which transmits DCI to theplurality of mobile station apparatuses 1 through a PDCCH, whenrespective bit numbers of a DCI format not including a carrier indicatorand a DCI format including the carrier indicator are the same as eachother, the base station apparatus 3 inserts 1 bit in the DCI formatincluding the carrier indicator, and the mobile station apparatus 1decodes the DCI format determining that 1 bit has been inserted in theDCI format including the carrier indicator.

It is to be noted that according to the present invention, theabove-described DCI format not including the carrier indicator and theDCI format including the carrier indicator may be the same DCI format.In addition, according to the present invention, when the respective bitnumbers of the DCI format allocated in the common search space and theDCI format allocated in the user equipment-specific search space are thesame as each other, the base station apparatus 3 inserts 1 bit in theDCI format allocated in the user equipment-specific search space, andthe mobile station apparatus 1 decodes the DCI format determining that 1bit has been inserted in the DCI format allocated in userequipment-specific search space.

In addition, according to the present invention, only when the DCIformat is allocated in the space where the common search space and theuser equipment-specific search space overlap with each other, the basestation apparatus 3 inserts a bit in the DCI format, and the mobilestation apparatus 1 decodes the DCI format determining that the bit hasbeen inserted in the DCI format. As a result of this, the mobile stationapparatus 1 can identify a type of the DCI format allocated in the spacewhere the common search space and the user equipment-specific searchspace overlap with each other from a difference in the bit number of theDCI format, i.e., a difference of a decoding method.

Second Embodiment

Hereinafter, a second embodiment of the present invention will bedescribed in detail with reference to the drawings.

In the second embodiment of the present invention, when the commonsearch space and the user equipment-specific search space overlap witheach other, and the bit numbers of the DCI format allocated in thecommon search space and the DCI format allocated in the userequipment-specific search space are the same as each other, the basestation apparatus 3 does not allocate the DCI format allocated in theuser equipment-specific search space in the overlapped space, and themobile station apparatus 1 performs blind decoding in the overlappedspace only of the DCI format allocated in the common search space.

For example, when allocating the DCI format 0/1A of 40 bit in the commonsearch space, and allocating the DCI format 2 of 40 bit and the DCIformat 0A of 41 bit in the user equipment-specific search space, thebase station apparatus 3 allocates the DCI format 0/1A and the DCIformat 0A in the space where the common search space and the mobilestation apparatus search space overlap with each other, and does notallocate the DCI format 2 of the same bit number as the DCI format 0/1Aallocated in the common search space, and the mobile station apparatus 1performs blind decoding of the DCI format 0/1A and the DCI format 0A inthe space where the common search space and the mobile station apparatussearch space overlap with each other, and does not perform blinddecoding of the DCI format 2 of the same bit number as the DCI format0/1A allocated in the common search space.

When compared a wireless communication system according to theembodiment with the wireless communication system according to the firstembodiment, there is a difference in the higher layer processing unit101 of the base station apparatus 3 and the higher layer processing unit201 of the mobile station apparatus 1. However, since configurations andfunctions of the other components are the same as in the firstembodiment, a description of the same functions as in the firstembodiment is omitted.

The DCI generation unit 1015 of the higher layer processing unit 101 ofthe base station apparatus 3 of the second embodiment does not insert abit in a DCI format based on the flow chart of FIG. 6. In addition, thescheduling unit 1013 of the higher layer processing unit 101 controlsthe transmission unit 107 through the control unit 103 so as not toallocate the DCI format allocated in the user equipment-specific searchspace of the same bit number as the DCI format allocated in the commonsearch space in the space where the common search space and the userequipment-specific search space overlap with each other.

The blind decoding control unit 2015 of the higher layer processing unit201 of the mobile station apparatus 1 of the second embodiment does notcalculate a bit number determining that the bit has been inserted in theDCI format based on the flow chart of FIG. 6. In addition, the blinddecoding control unit 2015 controls the reception unit 205 through thecontrol unit 203 so that the reception unit 205 may not perform blinddecoding of the DCI format allocated in the user equipment-specificsearch space of the same bit number as the DCI format allocated in thecommon search space in the space where the common search space and theuser equipment-specific search space overlap with each other.

As a result of this, the mobile station apparatus 1 can identify a typeof a DCI format allocated in the common search space and the userequipment-specific search space.

Third Embodiment

Hereinafter, a third embodiment of the present invention will bedescribed in detail with reference to the drawings.

FIG. 9 is a schematic diagram showing one example of a search spaceaccording to the third embodiment of the present invention. In the thirdembodiment of the present invention, when the common search space andthe user equipment-specific search space overlap with each other as aPDCCH candidate comprised of CCEs of No. 8 to No. 15 in FIG. 9 (PDCCHcandidate hatched with net-like lines of FIG. 9) (T100), the mobilestation apparatus 1 and the base station apparatus 3 change a PDCCHcandidate configuring the user equipment-specific search space from thePDCCH candidate of the user equipment-specific search space whichoverlaps with the common search space to a PDCCH candidate comprised ofCCEs of No. 24 to No. 31 which are not included in the common searchspace (T101).

When compared a wireless communication system according to theembodiment with the wireless communication system according to thefirst, embodiment, there is a difference in the higher layer processingunit 101 of the base station apparatus 3 and the higher layer processingunit 201 of the mobile station apparatus 1. However, sinceconfigurations and functions of the other components are the same as inthe first embodiment, a description of the same functions as in thefirst embodiment is omitted.

The DCI generation unit 1015 of the higher layer processing unit 101 ofthe base station apparatus 3 of the second embodiment does not insert abit in a DCI format based on the flow chart of FIG. 6. In addition, whenthe common search space and the user equipment-specific search spaceoverlap with each other the scheduling unit 1013 of the higher layerprocessing unit 101 changes a PDCCH candidate configuring the userequipment-specific search space from a PDCCH candidate of the userequipment-specific search space which overlaps with the common searchspace to a PDCCH candidate which is not included in the common searchspace.

The blind decoding control unit 2015 of the higher layer processing unit201 of the mobile station apparatus 1 of the second embodiment does notcalculate a bit number determining that the bit has been inserted in theDCI format based on the flow chart of FIG. 6. In addition, when thecommon search space and the user equipment-specific search space overlapwith each other, the blind decoding control unit 2015 changes a PDCCHcandidate configuring the user equipment-specific search space from aPDCCH candidate of the user equipment-specific search space whichoverlaps with the common search space to a PDCCH candidate which is notincluded in the common search space.

As a result of this, since the mobile station apparatus 1 can identifythe type of the DCI format allocated in the common search space and theuser equipment-specific search space without inserting a bit in the DCIformat as in the first embodiment, it can keep low a coding rate of thePDCCH, the DCI, or the DCI format. In addition, since the PDCCHcandidate is not limited in which the DCI format allocated in the userequipment-specific search space and with the same bit number as the DCIformat allocated in the common search space can be allocated as in thesecond embodiment, a degree of freedom of allocation of a DCI format iskept.

Hereinafter, a modified example of a third embodiment of the presentinvention will be described in detail with reference to the drawings.

In the modified example of the third embodiment of the presentinvention, the mobile station apparatus 1 and the base station apparatus3 do not include a PDCCH candidate comprised of CCEs of No. 0 to No. 15configuring the common search space of FIG. 9 in the userequipment-specific search spaces in which the number of CCEs configuringthe PDCCH candidate is the same 4 or 8 as in the common search space.

Specifically, a CCE and a PDCCH candidate configuring the userequipment-specific search space can be calculated by inputting in ahashing function C-RNTI having assigned to the mobile station apparatus1 and the number for identifying a subframe, etc. In the modifiedexample of the third embodiment, in deciding the user equipment-specificsearch spaces in which the number of CCEs configuring the PDCCHcandidate is the same 4 or 8 as in the common search space, the mobilestation apparatus 1 and the base station apparatus 3 decides a userequipment-specific search space from the CCEs of No. 16 to No. 47excluding No. 0 to No. 15 of FIG. 9, and in deciding a userequipment-specific search spaces in which the number of CCEs configuringthe PDCCH candidate is 1 and 2 different from the common search space,the mobile station apparatus and the base station apparatus 3 decides auser equipment-specific search space from all the CCEs of No. 0 to No.47 of FIG. 9.

There is the following difference between the third embodiment and themodified example of the third embodiment: in the third embodiment, themobile station apparatus 1 and the base station apparatus 3 decide auser equipment-specific search space from all the CCEs, and change theuser equipment-specific search space so that the common search space andthe user equipment-specific search space may not overlap with each otherwhen the common search space and the user equipment-specific searchspace overlap with each other; while in the modified example of thethird embodiment, in deciding a user equipment-specific search spaces inwhich the number of CCEs configuring the PDCCH candidate is the same asthat of the common search space, the mobile station apparatus 1 and thebase station apparatus 3 decides a user equipment-specific search spacefrom the CCEs excluding the CCE used for the common search space so thatthe common search space and the user equipment-specific search space maynot overlap with each other.

As a result of this, since the mobile station apparatus 1 can identifythe type of the DCI format allocated in the common search space and theuser equipment-specific search space without inserting a bit in the DCIformat as in the first embodiment, it can keep low a coding rate of thePDCCH, the DCI, or the DCI format. In addition, since the PDCCHcandidate is not limited in which the DCI format allocated in the userequipment-specific search space and with the same bit number as the DCIformat allocated in the common search space can be allocated as in thesecond embodiment, a degree of freedom of allocation of a DCI format iskept.

A program that operates in the base station apparatus 3 and the mobilestation apparatus 1 according to the present invention may be theprogram (program that makes a computer operate) that controls a CPU(Central Processing Unit) etc. so as to achieve a function in theabove-mentioned embodiment according to the present invention.Additionally, information dealt with in these apparatuses is temporarilystored in RAM (Random Access Memory) at the time of processing thereof,subsequently stored in various ROMs, such as a Flash ROM (Read OnlyMemory), and a HDD (Hard Disk Drive), and the information is read,corrected/written by the CPU if needed.

Note that a part of the mobile station apparatus 1 and the base stationapparatus 3 in the above-mentioned embodiment may be achieved with acomputer. In that case, the computer may be achieved by recording aprogram for achieving the above-described control function in acomputer-readable recording medium, and making the program recorded inthis recording medium read in a computer system to be executed. Notethat a “computer system” referred to herein is defined to be thecomputer system incorporated in the mobile station apparatus 1 or thebase station apparatus 3, and to include hardwares, such as an OS and aperipheral device.

In addition, a “computer-readable recording medium” means a portablemedium, such as a flexible disk, a magnetic optical disk, a ROM, and aCD-ROM, and a memory storage incorporated in the computer system, suchas a hard disk. Further, the “computer-readable recording medium” mayalso include a medium that dynamically holds a program for a short timeas a communication wire used when the program is transmitted through acommunication line, such as a network like the Internet, and a telephoneline, and a medium that holds a program for a certain time as a volatilememory inside the computer system serving as a server or a client whenthe program is dynamically held for the short time. In addition, theabove-described program may be the program for achieving a part of theabove-mentioned function, and it may be the program in which theabove-mentioned function can be achieved in combination with the programhaving been already recorded in the computer system.

In addition, a part or all of the mobile station apparatus 1 and thebase station apparatus 3 in the above-mentioned embodiment may beachieved as an LSI, which typically is an integrated circuit. Eachfunctional block of the mobile station apparatus 1 and the base stationapparatus 3 may be formed into chips individually, or some or all ofthem may be integrated to form a chip. In addition, a technique formaking the functional blocks into an integrated circuit may be achievednot only as the LSI but as a dedicated circuit or a general-purposeprocessor. In addition, when a technology for making the functionalblocks into the integrated circuit as an alternative to the LSI appearsdue to progress of a semiconductor technology, it is also possible touse an integrated circuit made by the technology.

(A) In addition, the invention in this application can employ thefollowing aspect. Namely, a wireless communication system of the presentinvention is the wireless communication system comprising a mobilestation apparatus and a base station apparatus which transmits controlinformation to the mobile station apparatus, wherein when an informationbit number of a first format which is the format of the controlinformation, and which includes information indicating a CC is apredetermined bit number, the base station apparatus inserts at least 1bit in the first format to decide a first payload size, and transmitsthe first format of the first payload size to the mobile stationapparatus, and the mobile station apparatus performs receptionprocessing of the first format determining that the first format is thefirst payload size.

(B) In addition, in the wireless communication system of the presentinvention, the predetermined bit number is a bit number of a payloadsize of a second format which is the format of the control informationand which does not include information indicating a CC.

(C) In addition, in the wireless communication system of the presentinvention, the first format is the format including informationindicating a CC in the second format.

(D) In addition, in the wireless communication system of the presentinvention, the second format is allocated in a common search space, andthe first format is allocated in a user equipment-specific search space.

(E) In addition, in the wireless communication system of the presentinvention, when allocating the first format in a space where the commonsearch space and the user equipment-specific search space overlap witheach other, the base station apparatus inserts a bit in the firstformat, and when the first format is allocated in the space where thecommon search space and the user equipment-specific search space overlapwith each other, the mobile station apparatus performs receptionprocessing determining that the bit has been inserted in the secondformat.

(F) In addition, in the wireless communication system of the presentinvention, the first format and the second format are controlinformation transmitted to the same mobile station apparatus.

(G) In addition, a wireless communication system of the presentinvention is the wireless communication system comprising a mobilestation apparatus and a base station apparatus which transmits controlinformation to the mobile station apparatus, wherein when a bit numberof a first format which is the format of the control information andwhich is allocated in a common search space, and a bit number of asecond format which is the format of the control information and whichis allocated in a user equipment-specific search space are the same aseach other, the base station apparatus does not allocate the secondformat but allocates only the first format in a space where the commonsearch space and the user equipment-specific search space overlap witheach other, and transmits the first format, and when the bit number ofthe first format which is the format of the control information andwhich is allocated in the common search space, and the bit number of thesecond format which is the format of the control information and whichis allocated only in the user equipment-specific search space are thesame as each other, the mobile station apparatus does not performreception processing of the second format, but only performs receptionprocessing of the first format in the space where the common searchspace and the user equipment-specific search space overlap with eachother.

(H) In addition, a wireless communication system of the presentinvention is the wireless communication system comprising a mobilestation apparatus and a base station apparatus which transmits controlinformation to the mobile station apparatus, wherein the base stationapparatus and the mobile station apparatus configure a common searchspace from a predetermined CCE, configure a user equipment-specificsearch space in which the number of CCEs configuring a PDCCH candidateis the same as that of a common search space from the CCEs excluding theCCEs used for the common search space, and configure from all the CCEsthe user equipment-specific search space in which the number of CCEsconfiguring the PDCCH candidate is different from that of the commonsearch space.

(I) In addition, a base station apparatus of the present invention isthe base station apparatus which transmits control information to amobile station apparatus, wherein when an information bit number of afirst format which is the format of the control information, and whichincludes information indicating a CC is a predetermined bit number, thebase station apparatus inserts at least 1 bit in the first format todecide a first payload size, and transmits the first format of the firstpayload size to the mobile station apparatus,

(J) In addition, a base station apparatus of the present invention isthe base station apparatus which transmits control information to amobile station apparatus, wherein when a bit number of a first formatwhich is the format of the control information and which is allocated ina common search space, and a bit number of a second format which is theformat of the control information and which is allocated in a userequipment-specific search space are the same as each other, the basestation apparatus does not allocate the second format but allocates onlythe first format in a space where the common search space and the userequipment-specific search space overlap with each other, and transmitsthe first format.

(K) In addition, a base station apparatus of the present invention isthe base station apparatus which transmits control information to amobile station apparatus, wherein the base station apparatus configuresa common search space from a predetermined CCE, configures a userequipment-specific search space in which the number of CCEs configuringa PDCCH candidate is the same as that of a common search space from theCCEs excluding the CCEs used for the common search space, and configuresfrom all the CCEs the user equipment-specific search space in which thenumber of the CCEs configuring the PDCCH candidate is different fromthat of the common search space.

(L) In addition, a mobile station apparatus of the present invention isthe mobile station apparatus which receives control informationtransmitted from a base station apparatus, wherein the mobile stationapparatus receives a first format determining that the first formatwhich is the format of the control information and which includesinformation indicating a CC is a first payload size decided by the basestation apparatus inserting at least 1 bit in the first format.

(M) In addition, a mobile station apparatus of the present invention isthe mobile station apparatus which receives control informationtransmitted from a base station apparatus, wherein when a bit number ofa first format which is the format of the control information and whichis allocated in a common search space, and a bit number of a secondformat which is the format of the control information and which isallocated only in a user equipment-specific search space are the same aseach other, the mobile station apparatus does not perform receptionprocessing of the second format, but only performs reception processingof the first format in the space where the common search space and theuser equipment-specific search space overlap with each other.

(N) In addition, a mobile station apparatus of the present invention isthe mobile station apparatus which receives control informationtransmitted from a base station apparatus, wherein the mobile stationapparatus configures a common search space from a predetermined CCE,configures a user equipment-specific search space in which the number ofCCEs configuring a PDCCH candidate is the same as that of the commonsearch space from the CCEs excluding the CCEs used for the common searchspace, and configures from all the CCEs the user equipment-specificsearch space in which the number of the CCEs configuring the PDCCHcandidate is different from that of the common search space.

(O) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, and the wireless communication method comprises: means forinserting at least 1 bit in a first format to decide a first payloadsize; and means for transmitting the first format of the first payloadsize to the mobile station apparatus when an information bit number ofthe first format which is the format of the control information andwhich includes information indicating a CC is a predetermined bitnumber,

(P) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, and the wireless communication method comprises: means fornot allocating a second format but allocates only a first format in aspace where a common search space and a user equipment-specific searchspace overlap with each other; and means for transmitting the firstformat when a bit number of the first format which is the format of thecontrol information and which is allocated in the common search space,and a bit number of the second format which is the format of the controlinformation and which is allocated in the user equipment-specific searchspace are the same as each other.

(Q) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, and the wireless communication method comprises: means forconfiguring a common search space from a predetermined CCE; means forconfiguring a user equipment-specific search space in which the numberof CCEs configuring a PDCCH candidate is the same as that of the commonsearch space from the CCEs excluding the CCEs used for the common searchspace; and means for configuring from all the CCEs the userequipment-specific search space in which the number of the CCEsconfiguring the PDCCH candidate is different from that of the commonsearch space.

(R) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a mobile stationapparatus which receives control information transmitted from a basestation apparatus, and the wireless communication method comprises meansfor receiving a first format determining that the first format which isthe format of the control information and which includes informationindicating a CC is a first payload size decided by the base stationapparatus inserting at least 1 bit in the first format.

(S) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a mobile stationapparatus which receives control information transmitted from a basestation apparatus, and the wireless communication method comprises meansfor not performing reception processing of a second format, but onlyperforming reception processing of a first format in a space where acommon search space and a user equipment-specific search space overlapwith each other when a bit number of the first format which is theformat of the control information and which is allocated in the commonsearch space, and a bit number of the second format which is the formatof the control information and which is allocated only in the userequipment-specific search space are the same as each other.

(T) In addition, a wireless communication method of the presentinvention is the wireless communication method used for a mobile stationapparatus which receives control information transmitted from a basestation apparatus, and the wireless communication method comprises:means for configuring a common search space from a predetermined CCE;means for configuring a user equipment-specific search space in whichthe number of CCEs configuring a PDCCH candidate is the same as that ofthe common search space from the CCEs excluding the CCEs used for thecommon search space; and means for configuring from all the CCEs theuser equipment-specific search space in which the number of the CCEsconfiguring the PDCCH candidate is different from that of the commonsearch space.

(U) In addition, an integrated circuit of the present invention is theintegrated circuit used for a base station apparatus which transmitscontrol information to a mobile station apparatus, and the integratedcircuit comprises: means for inserting at least 1 bit in the firstformat to decide a first payload size; and means for transmitting thefirst format of the first payload size to the mobile station apparatuswhen an information bit number of the first format which is the formatof the control information and which includes information indicating aCC is a predetermined bit number.

(V) In addition, an integrated circuit of the present invention is theintegrated circuit used for a base station apparatus which transmitscontrol information to a mobile station apparatus, and the integratedcircuit comprises: means for not allocating a second format butallocates only a first format in a space where a common search space anda user equipment-specific search space overlap with each other; andmeans for transmitting the first format when a bit number of the firstformat which is the format of the control information and which isallocated in the common search space, and a bit number of the secondformat which is the format of the control information and which isallocated in the user equipment-specific search space are the same aseach other.

(W) In addition, an integrated circuit of the present invention is theintegrated circuit used for a base station apparatus which transmitscontrol information to a mobile station apparatus, and the integratedcircuit comprises: means for configuring a common search space from apredetermined CCE; means for configuring a user equipment-specificsearch space in which the number of CCEs configuring a PDCCH candidateis the same as that of the common search space from the CCEs excludingthe CCEs used for the common search space; and means for configuringfrom all the CCEs the user equipment-specific search space in which thenumber of the CCEs configuring the PDCCH candidate is different fromthat of the common search space.

(X) In addition, an integrated circuit of the present invention is theintegrated circuit used for a mobile station apparatus which receivescontrol information transmitted from a base station apparatus, and theintegrated circuit comprises means for receiving a first formatdetermining that the first format which is the format of the controlinformation and which includes information indicating a CC is a firstpayload size decided by the base station apparatus inserting at least 1bit in the first format.

(Y) In addition, an integrated circuit of the present invention is theintegrated circuit used for a mobile station apparatus which receivescontrol information transmitted from a base station apparatus, and theintegrated circuit comprises means for not performing receptionprocessing of a second format, but only performing reception processingof a first format in a space where a common search space and a userequipment-specific search space overlap with each other when a bitnumber of the first format which is the format of the controlinformation and which is allocated in the common search space, and a bitnumber of the second format which is the format of the controlinformation and which is allocated only in the user equipment-specificsearch space are the same as each other.

(Z) In addition, an integrated circuit of the present invention is theintegrated circuit used for a mobile station apparatus which receivescontrol information transmitted from a base station apparatus, and theintegrated circuit comprises: means for configuring a common searchspace from a predetermined CCE; means for configuring a userequipment-specific search space in which the number of CCEs configuringa PDCCH candidate is the same as that of the common search space fromthe CCEs excluding the CCEs used for the common search space; and meansfor configuring from all the CCEs the user equipment-specific searchspace in which the number of the CCEs configuring the PDCCH candidate isdifferent from that of the common search space.

As described above, although one embodiment of the present invention hasbeen described in detail with reference to the drawings, a specificconfiguration is not limited to the above, and various changes of adesign etc. can be made without departing from the scope of the presentinvention.

DESCRIPTION OF SYMBOLS

-   1 (1A, 1B, and 1C) MOBILE STATION APPARATUS-   3 BASE STATION APPARATUS-   101 HIGHER LAYER PROCESSING UNIT-   103 CONTROL UNIT-   105 RECEPTION UNIT-   107 TRANSMISSION UNIT-   110 109 CHANNEL MEASUREMENT UNIT-   201 HIGHER LAYER PROCESSING UNIT-   203 CONTROL UNIT-   205 RECEPTION UNIT-   207 TRANSMISSION UNIT-   209 CHANNEL MEASUREMENT UNIT-   1013 SCHEDULING UNIT-   1015 DCI GENERATION UNIT-   2013 SCHEDULING UNIT-   2015 BLIND DECODING CONTROL UNIT

1-28. (canceled) 29-35. (canceled) 36-42. (canceled)
 43. A wirelesscommunication system comprising a mobile station apparatus and a basestation apparatus which transmits control information to said mobilestation apparatus, wherein said base station apparatus allocates controlinformation only in a physical downlink control channel candidate of acommon search space, and transmits said control information in case thatpayload sizes of the respective control information of the physicaldownlink control channel candidate of said common search space and aphysical downlink control channel candidate of a user equipment-specificsearch space, the physical downlink control channel candidates being thecandidates in which said control information is allocated, are the sameas each other, and the physical downlink control channel candidate ofsaid common search space and the physical downlink control channelcandidate of said user equipment-specific search space are comprised ofcontrol channel elements with same numbers, said mobile stationapparatus performs reception processing of said control informationdetermining that said control information has been transmitted using thephysical downlink control channel only in said common search space. 44.A base station apparatus comprising, a multiplexing unit configured toallocate control information only in a physical downlink control channelcandidate of a common search space in case that payload sizes ofrespective control information of the physical downlink control channelcandidate of said common search space and a physical downlink controlchannel candidate of a user equipment-specific search space, thephysical downlink control channel candidates being the candidates inwhich said control information is allocated, are the same as each other,and the physical downlink control channel candidate of said commonsearch space and the physical downlink control channel candidate of saiduser equipment-specific search space are comprised of control channelelements with same numbers, and a transmitting unit configured totransmit said control information to a mobile station apparatus.
 45. Thebase station apparatus according to claim 44, wherein CRC of saidcontrol information is scrambled by C-RNTI.
 46. The base stationapparatus according to claim 44, wherein said base station apparatuscommunicates with said mobile station apparatus using a plurality ofcomponent carriers, and control information which can be allocated insaid user equipment-specific search space includes informationindicating a component carrier to which said physical downlink controlchannel corresponds among said plurality of component carriers.
 47. Thebase station apparatus according to claim 44, wherein said base stationapparatus communicates with said mobile station apparatus using aplurality of component carriers, and said common search space and saiduser equipment-specific search space are configured in a same componentcarrier.
 48. A mobile station apparatus comprising: a receiving unitconfigured to perform reception processing of control informationdetermining that said control information has been transmitted using aphysical downlink control channel only in a common search space in casethat in said base station apparatus, payload sizes of respective controlinformation of the physical downlink control channel candidate of saidcommon search space and a physical downlink control channel candidate ofa user equipment-specific search space, the physical downlink controlchannel candidates being the candidates in which said controlinformation is allocated, are the same as each other, and the physicaldownlink control channel candidate of said common search space and thephysical downlink control channel candidate of said userequipment-specific search space are comprised of control channelelements with same numbers.
 49. The mobile station apparatus accordingto claim 48, wherein CRC of said control information is scrambled byC-RNTI.
 50. The mobile station apparatus according to claim 48, whereinsaid mobile station apparatus communicates with said base stationapparatus using a plurality of component carriers, and controlinformation which can be allocated in said user equipment-specificsearch space includes information indicating a component carrier towhich said physical downlink control channel corresponds among saidplurality of component carriers.
 51. The mobile station apparatusaccording to claim 48, wherein said mobile station apparatuscommunicates with said base station apparatus using a plurality ofcomponent carriers, and said common search space and said userequipment-specific search space are configured in a same componentcarrier.
 52. A wireless communication method used for a base stationapparatus which transmits control information to a mobile stationapparatus, wherein in case that payload sizes of respective controlinformation of a physical downlink control channel candidate of a commonsearch space and a physical downlink control channel candidate of a userequipment-specific search space, the physical downlink control channelcandidates being the candidates in which said control information isallocated, are the same as each other, and the physical downlink controlchannel candidate of said common search space and the physical downlinkcontrol channel candidate of said user equipment-specific search spaceare comprised of control channel elements with same numbers, said basestation apparatus allocates said control information only in thephysical downlink control channel candidate of said common search space,and transmits said control information.
 53. A wireless communicationmethod used for a mobile station apparatus which receives controlinformation transmitted from a base station apparatus, wherein in casethat in said base station apparatus, payload sizes of respective controlinformation of a physical downlink control channel candidate of a commonsearch space and a physical downlink control channel candidate of a userequipment-specific search space, the physical downlink control channelcandidates being the candidates in which said control information isallocated, are the same as each other, and the physical downlink controlchannel candidate of said common search space and the physical downlinkcontrol channel candidate of said user equipment-specific search spaceare comprised of control channel elements with same numbers, said mobilestation apparatus performs reception processing of said controlinformation determining that said control information has beentransmitted using the physical downlink control channel only in saidcommon search space.
 54. An integrated circuit used for a base stationapparatus which transmits control information to a mobile stationapparatus, wherein in case that payload sizes of respective controlinformation of a physical downlink control channel candidate of a commonsearch space and a physical downlink control channel candidate of a userequipment-specific search space, the physical downlink control channelcandidates being the candidates in which said control information isallocated, are the same as each other, and the physical downlink controlchannel candidate of said common search space and the physical downlinkcontrol channel candidate of said user equipment-specific search spaceare comprised of control channel elements with same numbers, said basestation apparatus allocates said control information only in thephysical downlink control channel candidate of said common search space,and transmits said control information.
 55. An integrated circuit usedfor a mobile station apparatus which receives control informationtransmitted from a base station apparatus, wherein in case that in saidbase station apparatus, payload sizes of respective control informationof a physical downlink control channel candidate of a common searchspace and a physical downlink control channel candidate of a userequipment-specific search space, the physical downlink control channelcandidates being the candidates in which said control information isallocated, are the same as each other, and the physical downlink controlchannel candidate of said common search space and the physical downlinkcontrol channel candidate of said user equipment-specific search spaceare comprised of control channel elements of same numbers, said mobilestation apparatus performs reception processing of said controlinformation determining that said control information has beentransmitted using the physical downlink control channel only in saidcommon search space.